Nonaqueous electrochemical cell with improved energy density

ABSTRACT

This invention relates to a nonaqueous cell comprising a lithium metallic foil anode and a cathode coating comprising iron disulfide as the active material wherein the coating is applied to at least one surface of a metallic substrate that functions as the cathode current collector. In particular, the cell of the within invention has improved performance on high rate discharge and is achieved, surprisingly, with an anode underbalance. The cell of the within invention has an anode to cathode input that is less than or equal to 1.0. We have discovered, unexpectedly, that the energy density for the cell both volumetrically and gravimetrically can be improved by approximately 20 to 25% while only increasing the volume of the cathode coating solids by approximately 10% through a unique and novel cathode coating formulation used in conjunction with a lithium foil anode.

More than one reissue application has been filed for the reissue of U.S.Pat. No. 7,157,185. The reissue applications are the present applicationand application Ser. No. 12/404,853, filed on Mar. 16, 2009. ApplicationSer. No. 12/404,853, now abandoned, is a continuation reissueapplication of the present reissue application.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/164,239, filed Jun. 5, 2002, entitled Non-aqueous ElectrochemicalCell with Improved Energy Density, now U.S. Pat. No. 6,849,360, which isincorporated herein by this reference.

FIELD OF THE INVENTION

This invention relates to a nonaqueous cell, such as a cell whereinlithium is the active anode material and iron disulfide or pyrite is theactive cathode material. More particularly, this invention relates tosuch a cell wherein the anode to cathode input ratio is less than orequal to 1.0.

BACKGROUND

The electrochemical couple of a lithium metal anode with a pyrite oriron disulfide cathode has long been recognized as a theoreticallyhigh-energy couple. Hereinafter, “pyrite” and “iron disulfide” will beused interchangeably. Lithium metal possesses the lowest density of anymetal and provides a volumetric energy density of 2062 mAh/cubiccentimeter and a gravimetric energy density of 3861.7 mAh/gram. Pyriteoffers advantageous energy opportunities as a result of its ability toundergo a four electron reduction, and has a volumetric energy densityof 4307 mAh/cubic centimeter and a gravimetric energy density of 893.58mAh/gram.

There are however many challenges in achieving a commercially viablecell with this particular electrochemical couple. One key challenge ishow to use internal cell volume efficiently. It is known that thiselectrochemical system results in a volume increase upon discharge andthe accompanying formation of reaction products. It is thereforenecessary that the cell design incorporate sufficient void volume toaccommodate this volume increase. It will be appreciated then, that asthe discharge efficiency of the cell increases, additional reactionproducts will be generated causing incremental volume increases thatmust be accommodated by the incorporation of sufficient void volumewithin the cell.

Attempts to improve the energy density of the cell by increasing thedensity of the cathode present additional challenges. First, it will beappreciated that an increase in the density of the cathode will resultin less void volume within this electrode to accommodate the reactionproducts, in turn requiring that alternative void sites within the cellbe provided. Further, the densification of the cathode through anincrease in the calendering force applied to the coated electrode stockcan result in a stretching of the metallic foil substrate mat functionsas the cathode current collector. Such stretching can compromise theuniformity of the coating layer and can lead to wrinkling, cracking andultimately the separation of all or portions of the coating layer fromthe substrate.

In the interest of accommodating the increase in volume relating to thereaction products for the lithium/iron disulfide electrochemical couplewhile also improving the cell discharge efficiency and cell capacity, itwill therefore be appreciated that the volume occupied by non-reactiveinternal cell components should be minimized to the extent possible. Inthis regard, use of lithium metal foil as the anode obviates the needfor a discrete anode current collector, since the lithium foil issufficiently conductive. However, lithium foil has a relatively lowtensile strength and as a result can undergo stretching and thinningcausing localized regions of reduced anode capacity. In a pronouncedcase, the thinning can be aggravated to the point of disconnects withinthe lithium anode. Various solutions to the problem of lithium foilweakness have been proposed, including, the design of cells with thickerlithium foils, separate anode current collectors, or lithium anodes withregions of reduced or non-ionic transport. These solutions typicallyresult in an anode overbalance in the cell and are not efficient orvolumetrically satisfactory. The use of excess lithium in the cell isalso costly since metallic lithium foil is a relatively costly material.

There is therefore a need for a nonaqueous lithium/iron disulfide cellwith an increased energy density and discharge efficiency thataccommodates the volume increase of the reaction products generatedduring discharge. There is further a need for such a nonaqueous cellhaving a dense cathode with good adhesion to the current collectorsubstrate without sacrificing the uniformity of the cathode coatinglayer. There is further a need for such a nonaqueous cell that reducesthe anode to cathode cell balance without sacrificing the integrity ofthe anode.

DRAWINGS

FIG. 1 is an illustration of an anode and a cathode and the interfacialelectrode width.

DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention relates to a nonaqueous cell comprising a lithiummetallic foil anode and a cathode coating comprising iron disulfide asthe active material wherein the coating is applied to at least onesurface of a metallic substrate that functions as the cathode currentcollector. In particular, the cell of the within invention has improvedperformance on high rate discharge and is achieved, surprisingly, withan anode underbalance. Said another way, the cell of the withininvention has an anode to cathode input ratio, as defined herein, thatis less than or equal to 1.0. We have discovered, unexpectedly, that theenergy density for the cell both volumetrically and gravimetrically canbe improved by approximately 20 to 25% while only increasing the volumeof the cathode coating solids by approximately 10% through a unique andnovel cathode coating formulation.

Preferably, the cathode coating formulation of the cell of the withininvention is used in conjunction with a lithium metallic foil anode. Thepreferred anode is a lithium-aluminum alloy. The aluminum content byweight is preferably between 0.1 and 2.0 percent, and still morepreferably is between 0.1 and 0.9 percent. In the preferred embodiment,the aluminum content of the lithium foil anode material is 0.5 percent.Such an alloy is available commercially from, by way of example,Chemetall Foote Corporation or FMC Corporation. We have found that theuse of this alloyed material in conjunction with the cathode slurryformulation described below, enables the amount of lithium utilized inthe cell to be minimized. The alloyed lithium results in an increase intensile strength. In a cell of the within invention where, for example,the electrodes are wound together into a jellyroll electrode assembly,the increase in tensile strength in the lithium aluminum alloytranslates into a material stretch of less than 0.5 percent over a 12.0inch initial electrode length. This in turn means that anodediscontinuities along the length of the wound electrode strip areminimized, contributing to an improvement in overall cell performance.We have also observed that the solid electrolyte interface film (or SEI)that forms during the initial reaction of the alloyed lithium anode withorganic solvents used in the electrolyte exhibits less ionic transferresistance than the SEI film that forms using an unalloyed lithiumanode.

The cathode slurry formulation of the cell of the within invention isnovel and unique in that it enables the creation of a denser cathode, ananode to cathode input ratio of 1.0 or less and an increase in the cellenergy density without sacrificing the discharge efficiency of the cellor the cathode integrity or the adhesion of the dried cathode slurry tothe metallic foil substrate. With regard to the cathode slurryformulation, we have discovered that proper selection of the conductiveadditives allows for a reduction in the amount of solvent utilized,resulting in a reduction of void volume in the final electrode coatingand a denser cathode. We have further discovered that through theincorporation of certain slip agents and rheological modifiers, thecalendering force required to achieve the desired cathode porosity andcoating thickness can be minimized, further enabling the anode tocathode input ratio of the cell of the within invention.

The preferred cathode slurry formulation of the cell of the withininvention comprises conductive carbon materials as additives.Preferably, the conductive carbon additives comprise a mixture ofsynthetic graphite and acetylene black. We have discovered that certainbeneficial effects can be achieved by incorporating a synthetic graphitethat is highly crystalline and possess an extreme anisotropic characterto provide a powder with a moderate to low surface area and structureand that also has a high purity level (hereinafter referred to as“highly crystalline synthetic graphite”). The moderate to low surfacearea and structure are characteristics of particular importance, asreflected in BET and DBP values as defined below, since we havediscovered that carbons with higher surface areas and structures tend toretain solvent, ultimately contributing to coating defects. A suitablehighly crystalline synthetic graphite has a maximum impurity or ashlevel of 0.1 percent, a mean particle size of 9 microns and a BETsurface area of approximately 10 m²/gm and a n-dibutyl phthalate, or DBPoil absorption ratio of 190 percent as per ASTM D2414 and is availablecommercially from Timcal Graphite as Timrex MX-15. “BET” refers to ASTMD6556, which correlates surface area with multipoint nitrogen gasadsorption. A preferred highly crystalline synthetic graphite has animpurity level of 0.01 to 0.2 percent, a mean particle size of 3.0 to11.0 microns, a BET surface area of 3.0 to 11.0 m²/gm and a DBP ratio of160 to 200 percent.

The acetylene black is preferably 55% compressed and is availablecommercially from, for example, Chevron under the product name acetyleneblack C55.

In the preferred cathode slurry formulation, the amount of conductivecarbon additives is from 7.0 to 11.0 volume percent of the total solidscontent and still more preferably is from 10.0 to 10.5 volume percent ofthe total solids content. The “solids content” and the “solids percent”as used herein refers to the dry cathode coating formulation withoutconsideration of the solvent, while the “wet content” and the “wetpercent” refers to the cathode coating formulation taking intoconsideration the solvent used. We have further discovered that indetermining the appropriate amount of carbon additives, the level ofhighly crystalline synthetic graphite should be maximized while thelevel of acetylene black should be minimized, to avoid undesiredelectrolyte retention that results in an increased difficulty inprocessing the electrode. Therefore, preferably the volume of highlycrystalline synthetic graphite exceeds the volume of acetylene black, onboth a wet and a dry or solids basis. Still more preferably, the volumeof highly crystalline synthetic graphite is at least twice the volume ofacetylene black, again on a wet and solids basis. In the preferredformulation, the solids volume percent of highly crystalline syntheticgraphite is between 7.0 and 7.5, while the solids volume percent ofacetylene black is between 3.0 and 3.5. Still more preferably, thesolids volume percent of highly crystalline synthetic graphite is 7.39and the solids volume percent of acetylene black is 3.05. On a solidsweight percent basis, acetylene black is preferably from 1.0 to 3.0percent, highly crystalline synthetic graphite is preferably from 3.0 to6.0 weight percent.

The preferred cathode slurry formulation of the within invention furthercomprises at least one rheological modifier to aid in electrodeprocessing. We have discovered that a cathode slurry comprising such amodifier with a high sensitivity to shear stress further enables thedense cathode and the anode to cathode input ratio of the cell of thewithin invention. Particularly desirable is an additive that will aidthe slurry in retaining its viscosity while in an undisturbed state butwill cause a drop in the slurry viscosity when the slurry is subjectedto a relatively high shear such as can be encountered during the processof transferring the slurry from a holding tank to the electrodesubstrate. The preferred modifier further aids the slurry in returningto the relatively higher viscosity once the shear stress is removed. Wehave discovered that the incorporation of fumed silica into the cathodeslurry of the cell of the within invention provides the above describedshear sensitivity. The preferred silica has a silanol group surfaceconcentration of between 0.5 and 1.0 mmol/gm, and most preferablybetween 0.70 and 0.80 mmol/gm. The fumed silica preferably is added inan amount of from 0.2 to 0.6 weight percent of the solids incorporatedinto the slurry formulation, with a bulk density of from 35.0 to 50.0gm/liter. A suitable fumed silica additive is available commerciallyfrom, for example, Degussa Corporation and is known as Aerosil 200,having a bulk density of 45.0 to 50.0 gms/liter. In a preferredformulation, the fumed silica comprises 0.3 weight percent of thesolids.

In the preferred cathode slurry formulation, micronized TEFLON®, ormicronized polytetrafluoroethylene (PTFE) is incorporated as a slipagent. The micronized TEFLON® preferably has a mean particle size of 2.0to 4.0 microns and a maximum particle size of 12.0 microns. Thepreferred micronized TEFLON® is easily dispersed in coating formulationsand has been processed to a 1.0 to 1.5 NPIRI grind, where NPIRI standsfor National Printing Ink Research Institute. Micronized TEFLON® ispreferably incorporated from 0.2 to 0.6 weight percent of the totalweight of the solids in the slurry, and still more preferably is addedat 0.3 weight percent. A suitable preferred micronized TEFLON® ismanufactured by MicroPowders Inc. and is available commercially fromDar-Tech Inc. under the name Fluo HT.

The anode to cathode input ratio as used herein can be calculated asfollows:

Anode Capacity Per Linear Inch:(foil thickness)×(interfacial electrode width)×1 inch×(density oflithium foil at 20° C.)×(lithium energy density, 3861.7 mAh/gm).Cathode Capacity Per Linear Inch:(final cathode coating thickness)×(interfacial electrode width)×1inch×(cathode dry mix density)×(final cathode packing percentage)×(dryweight percent FeS₂)×(percent purity FeS2)×(FeS₂ energy density, 893.58mAh/gm)Anode/cathode input ratio-anode capacity per linear inch/cathodecapacity per linear inch

“Interfacial electrode width” as used herein is the linear dimensionthat shares an interfacial area between the cathode and the anode. Anexample is illustrated in FIG. 1, where the dimension labeled “A” is theinterfacial electrode width. “Final cathode coating thickness” refers tothe coating thickness after any calendering operation or otherdensification processing of the cathode. “Final cathode packingpercentage” refers to the solid volume percentage after any calenderingoperation or other densification processing and is equivalent to 100percent less the void volume percentage after any calendering operationor other densification processing of the cathode. The “cathode dry mixdensity” refers to the additive density of the solid components of thecathode coating.

A preferred polymer binder for the cathode coating of the cell of thewithin invention is a styrene-ethylene/butylene-styrene (SEBS) blockcopolymer. One such suitable block copolymer is available commerciallyfrom Kraton Polymers of Houston, Tex. as Kraton G1651. The preferredsolvent for use with such a binder is stabilized1,1,2-trichloroethylene. One of skill in the art will appreciate thatother combinations of binders and/or solvents may be utilized in thecathode coating of the cell of the within invention without departingfrom the scope of the within invention

EXAMPLE

An electrochemical cell comprising lithium as the active anode materialand pyrite as the active cathode material is constructed as follows. Acontinuous strip of lithium metal foil 0.006 inches thick by 1.535inches wide and alloyed at 0.5 weight percent with aluminum is provided.An aluminum cathode current collector continuous strip 0.001 inchesthick by 1.72 inches wide is provided. The aluminum cathode collectorstrip is full hard standard alloy 1145-H19 aluminum and both surfacesare flame cleansed to remove oils and improve adhesion of the coating tothe substrate surface.

A cathode coating slurry is prepared using the following solids:

Material Weight percent (dry) cm³/100 gms FeS2 92.0 19.087 Acetyleneblack 1.4 0.733 Highly crystalline 4.0 1.777 synthetic graphite Formedsilica 0.3 0.136 Micronized PTFE 0.3 0.136 Kraton 2.0 2.198 24.067cm³/100 gms 4.155 gm/cm³

Cathode capacity per linear inch:(0.0063 in.)(1.535 in.)(1.0 in.)(16.387 cm³/in³) (4.1555 gm/cm³)(0.64solids packing) (0.92) (0.95)(893.58 mAh/gm )=329 mAh/linear inchAnode capacity per linear inch:(0.006 in.)(1.535 in.)(1.0 in.)(16.387 cm³/in³)(0.534 gm/cm³)(3861.7mAh/gm)=311 mAh/linear inchThe resulting anode to cathode input ratio is 311/329=0.95.

The anode, cathode and a suitable separator are wound together fromcontinuous webs into an electrode assembly with an overwrap on theexterior of the jelly roll and disposed within a can or other suitablecontainer. A plastic insulating disc is punched and placed into each caninitially. Automatic winders initiate the jellyroll with separator,followed by the cathode. The anode is introduced into the winder afterthe cathode and the jellyroll is formed to predetermined electrodelengths based on the location of the anode tab. The winder feed stock isseparated from the web and an overwrap film is introduced into thewinder at the trail end of the jellyroll and wound over the jellyrolluntil a predetermined jellyroll diameter is obtained. The wrap is cutand heat sealed, the cathode collector is crimped and the jellyroll isinserted into the container. The can is swaged to reduce its diameterprior to electrolyte filling.

Conventional cell assembly and closing methods are utilized to completethe final cell, followed by a predischarge regimen. The anode tab is a0.002 inch thick nickel plated steel foil tab that is pressure bonded tothe lithium foil web at predetermined intervals corresponding to thepredetermined prewind anode length of 12.00 inches and is bent over thecompleted jellyroll prior to insertion of the jellyroll into the can.The separator is a 25 micron thick polypropylene material available fromCelgard Corporation as Celgard 2400. The can is nickel plated steel withan outer diameter of 0.548 inches and the jellyroll finished diameter is0.525 inches. The outer wrap is a polypropylene film. The electrolyte is1.6 grams of 63.05 weight percent 1,3 dioxolane, 27.63 weight percent1,2 dimethoxyethane, 0.18 weight percent 3,5 dimethylisoxazole, and 9.14weight percent lithium iodide.

1. An electrochemical cell comprising a nonaqueous electrolyte, an anodeand a cathode assembly, the electrolyte comprising a solvent, thecathode assembly comprising a metallic cathode current collector havingtwo major surfaces and a cathode coating disposed on at least one of thetwo major surfaces, the coating comprising iron disulfide, and the anodecomprising metallic lithium, wherein the interfacial anode to cathodeinput ratio is less than or equal to 1.0.
 2. The cell of claim 1,wherein the metallic lithium is alloyed with aluminum.
 3. The cell ofclaim 2, wherein the metallic lithium comprises less than 1.0 percent byweight of aluminum.
 4. The cell of claim 3, wherein the metallic lithiumcomprises between 0.1 and 0.9 percent by weight aluminum.
 5. The cell ofclaim 4, wherein the metallic lithium comprises 0.5 percent by weight ofaluminum.
 6. The cell of claim 1, wherein the cathode coating furthercomprises a void volume of less than 43 percent.
 7. The cell of claim 6,wherein the void volume is from 36 percent to 42 percent.
 8. The cell ofclaim 7, wherein the cathode coating further comprises syntheticgraphite.
 9. The cell of claim 8, wherein the synthetic graphite ishighly crystalline synthetic graphite.
 10. The cell of claim 9, whereinthe highly crystalline synthetic graphite has a mean particle size of3.0 to 11.0 microns, a BET surface area of 3.0 to 11.0 m²/gm and ann-dibutyl phthalate oil absorption ratio of 160 to 200 percent.
 11. Thecell of claim 7, wherein the cathode coating further comprises acetyleneblack.
 12. The cell of claim 7, wherein the cathode coating furthercomprises a micronized polytetrafluoroethylene powder.
 13. The cell ofclaim 12, wherein the cathode coating further comprises astyrene-ethylene-butylene-styrene block copolymer.
 14. The cell of claim13, wherein the cathode coating further comprises fumed silica.
 15. Anelectrochemical cell comprising a nonaqueous electrolyte, an anode and acathode assembly, the cathode assembly comprising a metallic cathodecurrent collector having two major surfaces and a cathode coatingdisposed on at least one of the two major surfaces, the cathode coatingcomprising iron disulfide, fumed silica, acetylene black and syntheticgraphite, and the anode comprising metallic lithium.
 16. The cell ofclaim 15, wherein the synthetic graphite and the acetylene blacktogether comprise between 7.0 and 11.0 volume percent of the totalsolids content of the cathode coating.
 17. The cell of claim 16, whereinthe synthetic graphite and the acetylene black together comprise between10.0 and 10.5 volume percent of the total solids content of the cathodecoating.
 18. The cell of claim 17, wherein the solids volume percent ofthe synthetic graphite is at least twice the solids volume percent ofthe acetylene black.
 19. The cell of claim 15, wherein the syntheticgraphite has a mean particle size of 3.0 to 11.0 microns, a BET surfacearea of 3.0 to 11.0 m²/gm and an n-dibutyl phthalate oil absorptionratio of 160 to 200 percent.
 20. The cell of claim 15, wherein thecathode coating further comprises a micronized polytetrafluoroethylenepowder.
 21. The cell of claim 20, wherein the cathode coating furthercomprises a styrene-ethylene-butylene-styrene block copolymer.
 22. Thecell of claim 15, wherein the metallic lithium is alloyed with aluminum.23. The cell of claim 18, wherein the cathode coating further comprisesmicronized polytetrafluoroethylene, and astyrene-ethylene-butylene-styrene block copolymer, and the syntheticgraphite comprises highly crystalline synthetic graphite.
 24. The cellof claim 23, wherein the cathode components are present in the followingsolids weight percents: iron disulfide 90.0 to 94.0 percent; acetyleneblack 1.0 to 3.0 percent; synthetic graphite 3.0 to 6.0 percent;polytetrafluoroethylene 0.2 to 0.6 percent; silica 0.2 to 0.6 percent;SEBS block copolymer 1.5 to 3.0 percent.
 25. The cell of claim 2,wherein the cathode coating has a void volume of less than 43 percent.26. The cell of claim 1, wherein the anode to cathode input ratio isless than or equal to 0.95.
 27. The cell of claim 1, wherein the cathodecoating further comprises a conductive carbon material.
 28. The cell ofclaim 27, wherein the conductive carbon material is synthetic graphite.29. The cell of claim 28, wherein the synthetic graphite is highlycrystalline synthetic graphite.
 30. The cell of claim 27, wherein theconductive carbon material is acetylene black.
 31. The cell of claim 1,wherein the cathode coating further comprises a rheological modifier.32. The cell of claim 31, wherein the rheological modifier comprises asilanol group.
 33. An electrochemical cell comprising: a nonaqueouselectrolyte comprising at least one solvent; a jellyroll electrodeassembly having an anode and a cathode assembly wound together; whereinthe cathode assembly comprises a metallic cathode current collector withtwo major surfaces and a cathode coating comprising iron disulfidedisposed on at least one of said two major surfaces; and wherein theanode comprises metallic lithium; and wherein an interfacial anode tocathode input ratio for the jellyroll electrode assembly is less than1.0.
 34. The electrochemical cell according to claim 33, wherein theanode to cathode input ratio is less than or equal to 0.95.
 35. Theelectrochemical cell according to claim 33, wherein the metallic lithiumis alloyed with aluminum.
 36. The electrochemical cell according toclaim 35, wherein the anode to cathode input ratio is less than or equalto 0.95.
 37. The electrochemical cell according to claim 35, wherein theanode comprises between about 0.1 and 2.0 percent by weight of aluminum.38. The electrochemical cell according to claim 33, wherein thejellyroll electrode assembly also has an outer wrap comprisingpolypropylene.
 39. The electrochemical cell according to claim 33,wherein the cathode coating has a void volume of less than 43 percent.40. The electrochemical cell according to claim 33, wherein the cathodecoating further comprises a conductive carbon material.
 41. The cell ofclaim 40, wherein the conductive carbon material is highly crystallinesynthetic graphite.
 42. The cell of claim 40, wherein the conductivecarbon material is acetylene black.
 43. The cell of claim 33, whereinthe cathode coating further comprises a rheological modifier.
 44. Thecell of claim 43, wherein the rheological modifier comprises a silanolgroup.
 45. The cell of claim 33, wherein the jellyroll electrodeassembly has a diameter of at least about 0.525 inches.
 46. The cell ofclaim 33, wherein the jellyroll electrode assembly further comprises ananode tab.
 47. The cell of claim 46, wherein the anode tab is bent overthe jellyroll electrode assembly.
 48. The cell of claim 1, wherein theinterfacial anode to cathode input ratio=anode capacity per linearinch/cathode capacity per linear inch; wherein the anode capacity perlinear inch=(foil thickness)×(interfacial electrode width)×(density oflithium foil at 20° C.)×(lithium energy density, 3861.7 mAh/g); andwherein the cathode capacity per linear inch=(final cathode coatingthickness)×(interfacial electrode width)×(cathode dry mixdensity)×(final cathode packing percentage)×(dry weight percent FeS₂)×(percent purity FeS ₂)×(FeS₂ energy density, 893.58 mAh/g).
 49. Thecell according to claim 48, wherein the metallic lithium is alloyed withaluminum.
 50. The cell according to claim 48, wherein the metalliclithium comprises less than 1.0 percent by weight of aluminum.
 51. Thecell according to claim 50, wherein the metallic lithium comprisesbetween 0.1 and 2.0 percent by weight of aluminum.
 52. The cellaccording to claim 51, wherein the metallic lithium comprises about 0.5percent by weight of aluminum.
 53. The cell according to claim 48,wherein the cathode coating further comprises a void volume of less than43 percent.
 54. The cell according to claim 56, wherein the void volumeis from 36 percent to 42 percent.
 55. The cell according to claim 48,wherein the cathode coating further comprises synthetic graphite. 56.The cell according to claim 55, wherein the synthetic graphite has amean particle size of 3.0 to 11.0 Pm, a BET surface area of 3.0 to 11.0m² /g, and a DBP of 160 to 200 percent.
 57. The cell according to claim48, wherein the cathode coating further comprises acetylene black. 58.The cell according to claim 48, wherein the cathode coating furthercomprises a micronized polytetrafluoroethylene powder.
 59. The cellaccording to claim 48, wherein the cathode coating further comprises astyrene-ethylene-butylenestyrene block copolymer.
 60. The cell accordingto claim 48, wherein the cathode coating further comprises fumed silica.61. The cell according to claim 48, wherein the cathode coating furthercomprises a total of between 7.0 and 11.0 percent synthetic graphite andacetylene black, based on the total solids content of the cathodecoating.
 62. The cell according to claim 48, wherein the syntheticgraphite and the acetylene black together comprise between 10.0 and 10.5volume percent of the total solids content of the cathode coating. 63.The cell according to claim 48, wherein the solids volume percent of thesynthetic graphite is at least twice the solids volume percent of theacetylene black.
 64. The cell according to claim 48, wherein theelectrolyte comprises an organic solvent.
 65. The cell according toclaim 48, wherein the cathode assembly and the anode are wound togetherinto a jellyroll electrode assembly.